A native of the Buffalo–Niagara Falls metropolitan area, Andreessen played little league football before playing for Lancaster High School,[1] where he was noted for his work ethic and won numerous accolades, including Defensive Player of the Year in Western New York.
[2] In his final year at Bryant, Andreessen was named an All-American after setting a school record with 112 tackles, ranking 8th in the FCS in 2022, and finishing third in career tackles in Bryant Bulldogs history.
[3][4] After going undrafted in the 2024 NFL Draft, Andreessen was signed by his hometown Buffalo Bills on May 11, 2024, after a successful rookie minicamp tryout.
[4] Andressen started the second game of the preseason after Matt Milano and Terrel Bernard were sidelined due to injury and precaution, respectively.
[9][10] Andreessen's number 44 has historically only rarely been issued to players, being reserved (but not retired) in honor of Elbert Dubenion, a key contributor during the Bills' American Football League era; the number has historically been only used in the preseason and granted to players not expected to make a regular season roster.